Alzheimer's disease is a devastating disorder which a significant amount of clinical and pathological data has been accumulated. With this information in hand, it is becoming more important to supplement our current understanding with molecular avenues of investigation that could identify specific cellular dysfunction and death. One such approach that has been proven useful in the past for studying cellular perturbations in neurodevelopment has been to examine endogenous brain peptides. The brain produces a very large number of such species, that can be isolated and sequenced rapidly. This provides an opportunity to screen large numbers of peptides and look for ones that display differential expression between the disease and normal controls. Targeting peptides as markers of Alzheimer's disease offers other advantages as the current molecular methodologies being employed for studying the disease cannot identify peptides. Also, as a class, peptides can have important physiological roles. The projects proposed in this application are designed to systemically profile the endogenous peptide populations of specific brain regions in Alzheimer's diseased and normal brains. Also, as a continuation of our preliminary studies, two peptides that show a large decline in orbital frontal gyrus in Alzheimer's disease brain will be sequenced. Once antibodies have been produced to purified material, immunostaining procedures will be employed to identify the cell type(s) that normally produce these peptides. Brain regions to be examined in this survey will be homogenized in 6M guanidine HC1 so that all proteases will be completely inactivated. After acidification and centrifugation, a crude peptide fraction will be recovered on a preparative reverse-phase cartridge. This crude peptide fraction will be separated using a "two dimensional" HPLC procedure, first employing ion-exchange separation with step elution, followed by reverse- phase peptide mapping. Past experience has shown that this approach will purify most peptides from brain tissue to homogeneity and it allows sufficient sensitivity to examine species of low abundance. The result of the above analysis is a peptide "fingerprint" of the tissue being studied and these fingerprints from normal and diseased brain tissues can be compared. This approach has the potential for identifying peptides whose expression are regionally altered in Alzheimer's disease. Such species, once identified, can serve as markers of the disease and they can be used as avenues for pursuing lesions that give rise to it.